UNIVERSITY  OF  CALIFORNIA   PUBLICATIONS 

IN 

AGRICULTURAL    SCIENCES 

Vol.  3,  No.  7,  pp.  131-134  March  15,  1918 


A  NEW  METHOD  OF  EXTRACTING  THE 
SOIL  SOLUTION 

(A  Preliminary  Communication) 


BY 

CHAS.  B.  LIPMAN 


While  studying,  in  1914,  some  of  the  data  obtained  by  Quincke 
in  measuring  the  forces  by  which  thin  water  films  are  held  by  tiny 
particles  of  solid  matter,  there  occurred  to  the  writer  a  new  possibility 
for  a  method  of  extracting  the  soil  solution  from  soils  with  optimum 
moisture  contents.  By  making  a  simple  calculation,  I  found  that  if 
Quincke's  figures  were  correct,  particles  of  .005  mm.  in  diameter  had 
the  power  of  holding  very  thin  films  of  water  with  a  force  equivalent 
to  about  300,000  lbs.  to  the  square  inch.  I  argued,  therefore,  that 
since  particles  of  .005  mm.  diameter  constitute  the  "clay"  fraction  in 
some  mechanical  analysis  systems  and  since  a  large  part  of  soil 
material  may  consist  of  much  larger  particles,  that  it  should  be 
possible  to  bring  to  bear  on  soils  by  pressure  apparatus  already  in 
existence  enough  force  to  separate  soil  particles  from  some  water, 
even  when  soils  contained  relatively  small  quantities  of  moisture.  It 
appeared  to  me,  moreover,  that  the  large  machines  used  in  engineering 
laboratories  for  testing  the  strength  of  materials  should  be  admirably 
adapted  to  the  task  of  expressing  water  from  soil  if  suitable  containers 
for  the  soil  are  employed.  With  this  idea  as  a  basis,  I  started,  in  the 
year  above  mentioned,  to  experiment  first  on  peat  soils  with  a  letter 
press  of  the  old  fashioned  sort  and  found  that  water  could  be  obtained 
with  it  from  peat  containing  40%  of  moisture.  I  then  proceeded  to 
have  made  a  special  perforated  brass  plate  for  the  bottom  of  an  iron 
casing  about  12  inches  long  and  about  6  inches  in  diameter.  A  quan- 
tity of  clay  adobe  soil  with  optimum  moisture  content  was  placed  in 


132  University  of  California  Publications  in  Agricultural  Sciences       [Vol.  3 

the  tube,  a  plate  placed  over  it  and  pressure  applied  in  a  machine  of 
a  capacity  of  200,000  lbs.  to  the  square  inch.    About  25  c.c.  of  liquid 
were  thus  obtained  from  eight  pounds  of  soil.     The  result  of  this  ex- 
periment was  unsatisfactory,  owing  to  the  small  amount  of  liquid 
obtained  from  a  soil  with  an  optimum  moisture  content.    I  determined, 
therefore,  to  use  a  tube  with  a  much  smaller  diameter  (1  to  2  inches), 
so  that  the  pressure  exerted  by  the  machine  could  be  concentrated 
on  as  small  a  surface  as  possible  and  thus  rendered  more  efficient. 
When  such  a  tube  was  made,  other  difficulties  were  encountered.     A 
few  months  later,  these  were  surmounted  and  revised  forms  of  appa- 
ratus were  thus  prepared  from  time  to  time  as  other  duties  permitted. 
No  form  of  these  was  satisfactory  even  though  I  had  demonstrated 
that  small  amounts  of  the  soil  solution  could  be  obtained  with  some 
of  them.    During  the  last  few  months,  however,  I  have  had  the  privi- 
lege of  the  counsel  of  Mr.  C.  T.  Wiskocil  of  the  Department  of  Civil 
Engineering   of  this   university,   who   has   designed   a   new   form   of 
pressure  tube  for  my  purposes.     Such  a  tube  was  made  up  and  we 
have  tried  it  out,  recently,  on  several  occasions  with  gratifying  results. 
In  the  case  of  a  very  fine  sandy  soil  containing  an  optimum  moisture 
percentage  (about  15%  by  weight),  nearly  two-thirds  of  the  moisture 
was  expressed  from  samples  of  300  to  400  grams  of  moist  soil.     In 
the  case  of  a  clay  loam  soil,  we  were  not  so  successful,  but  from  two 
or  three  samples  of  about  300  grams  each  of  such  a  soil  containing 
about  20%  of  moisture   (by  weight),  we  obtained  enough  of  the  soil 
solution  to  make  conductivity  measurements  and,  if  needed,  quanti- 
tative analyses.     Certain  difficulties  were  encountered  in  pressing  the 
clay  loam  soil,  which  did  not  obtain  in  the  case  of  the  fine  sand,  but 
these  were  also  surmounted  by  another  suggestion  originating  with 
Mr.  Wiskocil.     Even  now  we  find  that  our  apparatus  needs  to  be 
changed,  or  a  new  one  must  be  made  to  stand  pressure  in  excess  of 
50,000  lbs.  to  the  square  inch,  so  that  greater  efficiency  in  pressing 
clay  loams  and  clays  may  be  attained.     The  detailed  description  of 
our  apparatus,  and  of  the  results  of  conductivity  measurements  and 
analyses   of   the   solutions   obtained   are   reserved   for   description   in 
another  paper  in  which   due  credit  will  be  given  Mr.  Wiskocil  and 
Dr.  I).  D.  Way  nick  for  invaluable  assistance  rendered  in  connection 
with  these  matters. 

My  principal  objed  now  is  to  direct  the  attention  of  my  colleagues 
in  soil  investigations  <o  the  Fact  that,  after  nearly  four  years  of  desul- 
tory effort,   I   have  succeeded   in  demonstrating  that  direct  pressure 


1918]  Lipman:  A  New  Method  of  Extracting  the  Soil  Solution  133 

can  be  used  successfully  for  purposes  of  obtaining  the  soil  solution 
as  it  exists  in  relatively  thin  films  around  the  soil  particles.     The  pro- 
cedure is  rapid,  clean,  and  of  high  efficiency.    With  further  improve- 
ments in  apparatus  which  we  are  now  planning,  the  method  should 
supplant  all  other  methods  known  today,  including  even  the  Morgan 
procedure.1     None  of  the  other  methods  are  really  satisfactory  and 
even  that  of  Morgan  is  laborious  and  slow,  and  introduces  the  factor 
of  oil,  which  complicates  and  renders  it  extremely  time-consuming 
and  untidy.     Within  receut  months,  I  have  noted  in  the  literature 
that  attempts  have  been  made  by  Ramann,  Marz,  and  Bauer2  and  by 
Van  Zyl3  to  use  direct  pressure  as  I  have  done.     The  original  papers 
detailing  the  work  of  these  investigations  are  not  available  to  me, 
however,  and  I  am  almost  entirely  in  the  dark  as  to  the  details  of 
the  method  and,  in  one  case,  of  the  magnitude  of  the  pressures  em- 
ployed.    The  maximum  pressure  thus  far  exerted  in  my  method  has 
been  approximately  53,000  lbs.  to  the  square  inch,  whereas  Ramann 
and  his  associates  with  a  hydraulic  press  seem  to  have  used  only  about 
1500  lbs.  per  square  inch.     Moreover",  if  the  abstract  of  their  paper 
which  is  available  to  me  has  interpreted  the  authors  correctly,  their 
method  is  only  applicable  to  soils  made  up  of  very  fine  particles  or 
containing  much  organic  matter.     My  experience   has  always  been 
that  the  coarsest  soils  are  always  the  easiest  to  manage  in  expressing 
water  from  them.     Indeed,  until  recently,  the  fine  grained  soils,  as 
above  intimated,  gave  me  considerable  trouble,  because  they  would 
creep  out  of  the  container  in  fine  ribbons,  while  the  pressure  was 
being  applied.    Mr.  Wiskocil's  suggestion  of  a  thin  casing  of  sand  for 
the  fine  grained  loam  or  clay  loam  has  obviated  that  difficulty,  how- 
ever.    I  judge  from  my  experience,  moreover,  that  Ramann  and  his 
coworkers  must  have  used  very  wet  soil  or  they  could  not  possibly 
have  secured  solutions  from  them  at  the  low  pressure  mentioned.    The 
abstract  of  Van  Zyl's  paper  says  nothing  about  the  pressure  used  by 
him  and  the  manner  in  which  it  was  applied.     The  statement  is  that 
the  soil  can  be  "squeezed."     Other  comparisons  of  my  method  with 
the  comparable  ones  just  discussed  will  be  given  in  a  later  paper. 

Finally,  it  may  not  be  superfluous  to  emphasize  the  importance  to 
all  soil  studies  of  the  proper  use  of  the  method  which  I  have  described 
above.     It  allows  of  the  direct  determination  of  the  concentration  of 


i  Soil  Science,  vol.  3,  p.  531  (1917). 

2  Int.  Mitteil.  Boclenkunde,  vol.  6,  p.  27  (1916),  cited  from  Chem.  Abst.,  vol.  11, 
no.  22,  p.  3078  (1917). 

3  Jour.  Landw.,  vol.  64,  p.  201  (1916),  cited  from  E.  S.  E.,  vol.  36,  p.  720. 


134  University  of  California  Publications  in  Agricultural  Sciences        [Vol.3 

the  soil  solution,  and  of  the  amounts  of  each  of  the  solutes  contained 
therein.  It  renders  possible,  further,  such  studies  as  will  clarify  our 
vision  with  regard  to  the  relations,  if  any,  which  obtain  between  the 
soil  solution  and  soil  extracts  as  ordinarily  made.  It  permits  us  for 
the  first  time,  so  far  as  I  am  aware,  to  obtain  quickly  and  directly 
large  portions  of  the  soil  solution  as  it  exists  naturally  under  field 
conditions  when  crops  are  growing,  and  thus  to  correlate  these  solu- 
tions in  all  their  qualities  with  the  conditions  of  the  growing  crop. 
It  may  doubtless  be  the  means  of  throwing  much  light  on  the  methods 
for  making  nutrient  solutions  for  growing  plants,  and  probably  also 
on  many  obscure  problems  in  plant  physiological  pathology.  Indeed, 
the  possibilities  are  many  in  which  the  method  which  I  have  described 
for  obtaining  the  soil  solution  can  be  used  to  the  very  great  advantage 
of  soil  and  plant  studies. 

Transmitted  March  8,  1918. 


